<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {margin: 0; padding: 0;}
    .container {
      height: 100vh;
      display: flex;
      background-color: green;
    }
    .layout {
      background-color: red;
      display: flex;
      align-items: center;
      justify-content:center;
      flex: 1;
    }
    .box {
      width: 400px;
      height: 400px;
      border: 1px solid black;
      background-color: orange;
    }
  </style>
</head>
<body>
  <div class="container">
    <div class="layout">
      <div class="box"></div>
    </div>
  </div>
</body>
</html>